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How much do you know about austenitic stainless steel?

2022-04-25 Page view : 9 views

What is Austenitic Stainless Steel?

Austenitic stainless steel, which have been invented in Germany in 1913. It has been playing an important role in stainless steel. It refers to stainless steel with austenitic structure at room temperature. The austenite structure is stable when the content of Cr is about 18%, Ni is about 8%~10% and C is about 0.1%. Its production and usage account for about 70% of the total production and usage of stainless steel. The numbers of the steel are also the most, China commonly used austenitic stainless-steel brand has more than 40, the most common is 18-8 type. We are the leading Austenitic stainless-steel manufacturer.

 

Evolution of Austenitic Stainless Steel Brand Composition

Based on the composition of 18-8 stainless steel, there are major developments as following:

(1) Add Mo to improve pitting and crevice corrosion resistance

(2) Decrease C or add Ti and Nb to reduce intergranular corrosion tendency

(3) Add Ni and Cr to improve the high temperature oxidation resistance and strength

(4) Add Ni to improve stress corrosion resistance

(5) Add S,Se to improve machinability and component surface accuracy

Is 304 Stainless Steel Austenitic Stainless Steel?

304 stainless steel is austenitic stainless steel. High temperature resistance of 800 degrees, with good processing performance, high toughness, widely used in industry, furniture decoration industry, food and medical industry. 304 is a universal stainless steel, which is widely used to make equipment and parts requiring good comprehensive performance (corrosion resistance and formability). To maintain the corrosion resistance inherent in stainless steel, the steel must contain at least 18% chromium and at least 8% nickel. 304 stainless steel is a brand of stainless steel produced in accordance with ASTM standards in the United States.

Is Austenitic Stainless Steel Food Grade?

Austenitic stainless steel is not food grade stainless steel. Food grade refers to the austenitic stainless steel surface polishing and other processing, to ensure health and non-toxic. Food grade stainless steel refers to the “national standard of the People’s Republic of China/stainless steel tableware container health standard” GB 9684-88 provisions of stainless-steel material, its lead chromium content is much lower than general stainless steel. It requires food machinery to contact with food parts and must meet certain food safety requirements. Because food production process to use a lot of acid and alkali, and stainless steel contains chromium, unqualified stainless steel, will dissolve out of various prices of chromium, toxic. Moreover, it is required to limit the content of lead, cadmium and other alloy impurities.

Chemical Cleaning and Passivation of Austenitic Stainless Steels

Austenitic stainless-steel pickling and passivation are often done synchronously. People generally use the oxidizing strong nitric acid as the main agent of cleaning agent, such as the need of passivation equipment containing oil, organic matter and other substances, acid is not easy to dissolve in order to improve the quality of pickling and passivation membrane, request before passivation, degreasing cleaning are on the passivation treatment.

Corrosion of Austenitic Stainless Steel

For austenitic stainless steel, chloride solutions (mainly chloride ions) are its Nemesis. Austenitic stainless steel is prone to not only pitting corrosion, but also stress corrosion, gap corrosion and intergranular corrosion under heat. As austenitic stainless steel is widely used in daily life, stress corrosion, stress corrosion sensitivity after cold work hardening and high temperature embrittlement are the main failure problems. So, we should be in use according to the specific environmental conditions, in the selection of materials, design and technology to avoid the emergence of some problems.

Welding of Austenitic Stainless Steel

Using manual tungsten argon arc welding base, electrode arc welding filling and cover. Argon arc welding in the welding process of metal loss is small, due to the short arc welding quickly, linear stretch, decrease the times of arc, arc starting and avoid duplication of heat, low heat input, especially suitable for austenitic welding heat sensitive, easy penetration, argon gas protection, big drops of molten pool surface tension, forming good on the back of weld, the microstructure grain refinement, can meet the requirements of mechanical properties.